The invention relates to a drive arrangement for a motor vehicle having a four-wheel drive establishable by connecting one wheel axle with another drivable wheel axle and wherein the one wheel axle is drivable via an auxiliary drive shaft and a gear shift transmission, arranged in parallel with respect to its input shaft drive.
In the case of a known drive arrangement of this type having a connectable rear axle drive (Journal OFF ROAD, 1985, No. 4, page 34), the driving engine and a hydrodynamic torque converter are arranged in front of and a planetary gear shift transmission is arranged behind the front axle. The auxiliary drive shaft is arranged coaxially to the pinion shaft of the front axle differential gear, and at both shaft ends is equipped with a spur gear fixed with respect to it. The output shaft of the gear shift transmission that is penetrated by the input shaft, at its front shaft end facing the front axle, is equipped with a gear that mates with the front gear of the auxiliary drive shaft. A drive shaft that is coaxial to the input shaft leads to the rear axle drive and carries a gear mating with the rear gear of the auxiliary drive shaft. This gear, by means of a clutch, can be engaged with its drive shaft for driving of the rear axle drive. When the rear axle drive is not connected, the auxiliary drive shaft with the gear stage and the clutch for the connecting of the rear axle drive represent unutilized constructional expenditures.
From U.S. Pat. No. 3,908,775 to Van Fossen, it is known to shift the interaxle differential of a transfer case for a four-wheel drive, changing the drive as well as the output between two shifting stages. In one shifting stage for a balanced four-wheel drive, the output shaft of the differential is driven by the engine, while the two central gears of the transmission output are brought into driving connection with one drive shaft respectively. In the other shifting stage for an unbalanced four-wheel drive, the drive on the side of the engine takes place onto one central gear of the differential, the other central wheel of which is braked to a standstill. In this case, the output shaft rotates more slowly and drives both vehicle axles.
The instant invention is based on the objective of achieving a better utilization of the auxiliary drive shaft in the case of a drive arrangement of the above type.
An object of the invention is obtained by a drive arrangement for a motor vehicle having a four-wheel drive establishable by connecting one wheel axle with another drivable wheel axle, wherein the one wheel axle is drivable via an auxiliary drive shaft and a gear shift transmission, arranged in parallel to the axis of its input shaft and wherein the auxiliary drive shaft and input shaft can be brought into direct driving connection with one another by means of an auxiliary transmission. At least one of these input and auxiliary shafts are clutched into driving connection with the auxiliary transmission only when the torque transmission in the gear shift transmission is interrupted and an interaxle differential means that is connected between the two wheel axles is brought into an unblocked condition.
In the case of the drive arrangement according to the invention, it is possible to form a forward gear and/or a reverse gear independently of the gear shift transmission, i.e., without requiring any partial engagement transmission of the latter.
Another object of the invention is to provide at least two alternative auxiliary transmission paths between the input shaft and the auxiliary drive shaft.
Another object of the invention is to provide a third alternative auxiliary transmission path between the input shaft and the auxiliary drive shaft to provide for a reverse driving direction.
It is another object of the invention to provide for plural drive trains between an engine and auxiliary drive shaft utilizing a hydrodynamic flow converter, gearing transmission, interaxle differential and hollow drive shafts which will provide for 5 normal forward speeds, as well as a low forward speed and two reverse forward speeds.